Hall motor including means for selectively varying the effective number of turns of the exciting windings

ABSTRACT

A Hall motor utilizing Hall elements in place of the conventional commutators provides for speed variation with the motor efficiency unchanged. The motor comprises a control circuit having speed control switches and resistors. Speed control switches selectively switch the resistors into the control circuit which includes a transistor the base of which is controlled by the potential across the resistors. The motor further comprises driving transistors connected with exciting windings of the motor having intermediate taps. Switches are provided for selectively coupling the intermediate taps of the exciting windings to the driving transistors. Hall elements with their voltage terminals connected in the base circuits of the driving transistors are provided for varying the bias to the base circuits of the driving transistors. The speed control switches and the switches for selectively connecting the intermediate taps to the driving transistors are coupled in an interlocked relationship. In a modified form of the invention, the Hall motor includes double-pole double-throw switches for changing the flow direction of the exciting current passing through the exciting windings thus providing bidirectional operation as well as variable speed control.

Hanada [45] Mar. 21, 1972 1 1 HALL MOTOR INCLUDING MEANS 3,517,2896/1970 Brunner et al ..318/l38 FOR SELECTIVELY VARYING THE 3,518,5176/1970 Rainer ..318/l38 EFFECTIVE NUMBER OF TURNS OF THE EXCITINGWINDINGS 72] lnventor: Toshihide Hanada, Yokohama, Japan [73] Assignee:Pioneer Electronic Corporation, Tokyo,

Japan [22] Filed: June 24, 1970 [21] Appl. No.: 49,479

[30] Foreign Application Priority Date June 24, 1969 Japan ..44/493l9[52] U.S. Cl ..318/254, 310/189, 318/305, 318/337, 318/354, 318/347,318/502 [51] Int. Cl. ..H02k 29/00 [58] 318/345, 332, 347, 348, 254,318/138, 305, 337, 354, 502, 538, 531; 310/10 HR, 189

[ 56] References Cited UNITED STATES PATENTS 3,440,506 4/1969 Krestel eta1 ..318/254 X 3,159,777 12/1964 Manteuffel..... ...318/345 X 3,348,11310/1967 Vichr ...318/305 X 3,448,359 6/1969 Engel ..318/138 PrimaryExaminer-G. R. Simmons Attorney-Sughrue, Rothwell, Mion, Zinn & Macpeak[57] ABSTRACT A Hall motor utilizing Hall elements in place of theconventional commutators provides for speed variation with the motorefficiency'unchanged. The motor comprises a control circuit having speedcontrol switches and resistors. Speed control switches selectivelyswitch the resistors into the control circuit which includes atransistor the base of which is controlled by the potential across theresistors. The motor further comprises driving transistors connectedwith exciting windings of the motor having intermediate taps. Switchesare provided for selectively coupling the intermediate taps of theexciting windings to the driving transistors. Hall elements with theirvoltage terminals connected in the base circuits of the drivingtransistors are provided for varying the bias to the base circuits ofthe driving transistors. The speed control switches and the switches forselectively connecting the intermediate taps to the driving transistorsare coupled in an interlocked relationship.

In a modified form of the invention, the Hall motor includes double-poledouble-throw switches for changing the flow direction of the excitingcurrent passing through the exciting windings thus providingbidirectional operation as well as variable speed control.

4 Claims, 6 Drawing Figures PATENTEDM ARZI I972 SHEET 3 [IF 4 HALL MOTORINCLUDING MEANS FOR SELECTIVELY VARYING THE EFFECTIVE NUMBER OF TURNS OFTHE EXCITING WINDINGS BACKGROUND OF THE INVENTION This invention relatesto an electric motor and more particularly to a Hall motor whichutilizes Hall elements in place of commutators as in conventionalmotors.

In the prior art, Hall motors having a circuit structure as shown inFIG. 1 have been manufactured and used where it was desired to changethe motor speed or revolution rate. Such a prior art motor included acontrol circuit C having. speed control switches S, and 8,. In suchmotors, the speed can be changed simply by switching the positions ofswitches l creases, the control current flowing through the Hallelements H, and H in the Hall motor is increased. Because of this, a

Hall generation voltage increases causing the current which is flowingin the exciting windings or field windings W,, W W and W of the Hallmotor to increase, which in turn allows for an increase in the speed ofthe Hall motor. However, if

switches S, and S of the control circuit are switched so as to decreasethe collector current in transistor T the speed of the Hall motor willdecrease.

The prior art motor of FIG. 1 operates in accordance with I thecharacteristic curves shown in FIG. 2. This figure depicts a torque T ofthe Hall motor along the horizontal axis with respect to thecharacteristics of rotation frequency n, exciting current I andefficiency 1;, each of which is depicted on the vertical axis. The curvedesignated n is a fundamental rotation frequency torque characteristiccurve of a Hall motor. This corresponds to the situation where thecontrol circuit C is not connected. The rotation frequency torquecharacteristic curves n, and n represent two conditions where thecontrol circuit C is connected and operating. When the speed controlcharacteristic n, represents a possible situation if the switches S, andS, are switched to another position. However, even if S, and age s w itched, tl'g exci tjng current 12 has exactly the# same value as it hadbefore. Therefore, the exciting current torque characteristic curve forexciting current I, is identical to the exciting current torquecharacteristic for an exciting current I,. On the other hand, theefficiency varies. This is depicted as characteristic curve 1;, whichdiffers markedly from the efficiency torque curve 1 Thus, in the priorart Hall motors, a change in motor speed causes a variation inefficiency.

It is, therefore, an object of the present invention to provide a Hallmotor, the efficiency of which does not decrease even if there is achange in motor speed.

In addition, prior to the invention there has not been manufactured aHall motor which is bidirectional. Thus, it is another object of theinvention to provide a Hall motor which is bidirectional, that is, onewhich can be rotated in either a clockwise or counterclockwisedirection. It is a further object of the invention to provide a variablespeed, bidirectional Hall motor.

SUMMARY OF THE INVENTION As onefeature of the present invention, thereis provided a Hall motor which comprises a control circuit having speedcontrol switches and resistors forming a plurality of potential dividerswhich are selectively switched into the control circuit by means of thespeed control switches and a transistor the bias to the base of which isswitched by said switches, driving transistors connected to excitingwindings of the motor the 0 windings having intermediate taps, switchesfor switching the driving transistors to different ones of theintermediate taps and Hall elements with their voltage terminalsconnected with the base circuits of the driving transistors, said speedcontrol switches and the switches for selectively coupling the drivingtransistors to the different taps of the exciting windings being coupledin an interlocked relation.

Another feature of the present invention is that the foregoing Hallmotor includes double-pole double-throw switches for changing the flowdirection of the exciting current passing through the exciting windingsthereby providing for bidirectional operation.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an electric circuit diagramof a conventional variable speed Hall motor;

FIG. 2 shows several characteristic curves of the motor shown in FIG. 1relative to torque variation; 1

FIG. 3 shows several characteristic curves of a motor constructed inaccordance with the present invention relative to torque variation;

FIG. 4 is a basic circuit diagram of the motor according to the presentinvention;

FIG. 5 shows an embodiment of the variable speed type Hall motoraccording to the present invention; and

FIG. 6 shows an embodiment of the bidirectional, variable speed typeHall motor according to the present invention.

Description of the Preferred Embodiments Referring first to FIG. 4,transistors T, and T are part of the speed control circuit whiletransistors T,,, T, and T T correspond to the driving transistors. Thesedriving transistors derive their base voltages from their correspondingHall elements H, and H Exciting windings or field windings W, through Whave, respectively, intermediate taps 2, 3 connected to correspondingterminals of switches S 8,, S and S,,. The moveable contacts of switchesS through S are connected to the corresponding collectors of thetransistors T and T Diodes D, through D, have their anodes connected tothe corresponding collectors of the transistors T through T and theircathodes connected in parallel to a speed control transistor T,.Transistor T is connected at its base to the collector circuit of thetransistor T,. Thus, the base potential of transistor T is derived fromthe output of the collector transistor T The collector current of thetransistor T flows into the current terminals of the aforesaid Hallelements H, and H The Hall elements H, and H sense the magnetic fieldgenerated by the rotor of the motor and generate Hall voltages which aresupplied as a base voltage alternately to transistors T;,, T, and T T Inthis manner the transistors T, through T, generate alternating collectorvoltages to cause exciting current to flow into the exciting windings.

If the moveable contacts of the switches 8, through 8 are connected totheir respective terminals 1, exciting current flows through the entirelength of the exciting windings. Under such conditions the rotationfrequency-torque characteristic curve takes the form of curve n shown inFIG. 3. In this figure, the curve n,, represents the rotation frequencytorque characteristic when the control circuit is not connected. It isunderstood, however, that the motor does not operate under such a motoris given by the product of the torque and the number of revolutions(that is the output of the motor) divided by the product of the excitingcurrent and the line voltage (that is, the motor input). With the motoroperating according to the characteristic curve n the efficiency of themotor is represented by the curve 1 Assume that switches S through S ofthis motor are switched simultaneously (or under the control of theinterlocked relation therebetween) to shift to the respective taps 3. Asa result, the number of effective turns in each of the exciting windingsdecreases, so that, if the speed control circuit is absent, the rotationfrequency torque characteristic will change to the curve n However,since the speed control circuit is in actuality connected thecharacteristic curve for the rotation torque characteristic takes theform of curve n As is also known in the art, the torque T isproportional to the product of the armature current I,,, magnetic flux4:, and the number of turns in the exciting windings. This relationshipis given mathematically by the equation:

T=K N d) 1,, where K is a constant determined by the configuration ofthe motor. Therefore, when switches S through 5,, are switched,

the number of turns N decreases while K and 42 remain constant. Thus, inorder to produce the same torque as that produced prior to the switchingof the switches S, to S,,, the exciting current or 1,, has to beincreased by an. amount corresponding to the decreased part of thewinding turns. Thus, the current torque characteristic after havingswitched switches S to S varies along the curve I in FIG. 3. Theefficiency in this case is the product of the torque T and the rotationfrequency n divided by the product of the line voltage and the current 1and is represented by the curve 1;, in FIG. 3. Accordingly, if the valueof n versus n is determined by the manipulation of the control circuitso as to be proportional to the value of n versus n the values of 1;,and 1 become substantially identical. Therefore, irrespective of therotation frequency, it is possible to drive the motor at a highefficiency.

FIG. shows an example of the practical circuit in which the speedvariation feature is incorporated in accordance with the presentinvention. In this circuit, the bias circuit connected to the base oftransistor T in the speed control circuit is switched in the same manneras the prior art system, and the exciting windings of the presentinvention are also changed.

When the switches S through S are used to effect such switching actionthey are switched by means of an interlocked relationship so that thewinding turns of the exciting windings decrease at the same time thebias resistors R R and R are also switched to increase or decrease theresistance and the resistors R R and R are switched to decrease orincrease in resistance to give appropriate values. Thus, inconsequenceof the foregoing operation, it becomes clear that the speed can beincreased to reach a given value with the efficiency retainedsubstantially constant.

When the rotation frequency is to be decreased, this can be accomplishedby increasing the effective number of turns in the exciting windings.

FIG. 6 shows an example of the circuit which was designed for easy speedcontrol operation in addition to bidirectional operation. That is, thisembodiment can accomplish the speed variation action while operatingwith the rotor rotating either clockwise or counterclockwise.

To explain the operation of the circuit of FIG. 5 in more detail, theintermediate taps of the exciting windings W through W are connected,respectively, to the switches 8;, through 8,, as described above. Themoveable contacts of the respective switches S through S and the otherends of the exciting windings W through W. are connected, respectively,to the corresponding contacts a and b of the double-pole doublethrowswitches 5, through S with one of the poles of the DPDT switchesconnected to the B power source with the other one of the polesconnected to the corresponding collectors of transistors T through T Ifthe moveable contacts of the DPDT switches 8 through S are thrown to thea, I) contact side, the beginnings of the exciting windings connected tothe contacts a are connected to the B power source and the ends of theexciting windings connected through the switches S through 8., to therespective contacts b are connected to the corresponding collectors ofthe transistors T through T Thus, if the moveable contacts of theswitches 8, through S are thrown to the a, b contact side, thebeginnings of the exciting windings are connected to the transistors Tand T and the winding end of the exciting windings are connected to theB power source, so that, the flow direction of the exciting current inthe exciting windings is reversed thus, the rotating magnetic filedgenerated thereby rotates in the opposite direction with respect to theprevious direction, therefore, the rotor of the motor rotates in theopposite direction.

As was described hereinabove, the double-pole doublethrow switches Sthrough S are switched in interlocking relation. In addition, the changeof the rotation frequency is accomplished simply by switching theswitches 5, through S thereby effecting speed variation whilemaintaining the efficiency of substantially constant value.

As is appreciated from the foregoing description, in accordance with thepresent invention there has been provided the Hall motor having theaforesaid structure. The present invention Hall motor can accomplishadjustment of the rotation frequency without resulting in a variation ofefficiency, and in addition provides for bidirectional operation whichhas heretofore been unattained with prior art Hall motors. Accordingly,it is clear that the present motor has high efficiency and varies in itsuse-due to the combination of bidirectionality and the capability ofvariable speed control. Thus, the present Hall motor is very suitablefor use as a motor for tape recorders which are required to have forwardnormal speed, forward fast speed, reverse normal speed, and reverse fastspeed functions. While the preferred embodiments of the invention havebeen described herein, it is to be appreciated that variations andmodifications may be made without departing from the spirit of theinvention.

I claim:

1. A Hall motor of the type having a plurality of exciting windings,driving transistors for driving said windings and Hall elements forvarying the bias to the base circuits of said driving transistors, theinvention comprising,

a. control means, including means for varying the control currentflowing in the Hall elements, to control the speed of said motor, and

b. means coupled to said exciting windings for varying the effectivenumber of turns of said exciting windings in response to desired speedvariations to compensate for the loss in efficiency on the variation ofmotor speed.

2. The Hall motor of claim I wherein said control means furtherincludes, a plurality of voltage divider circuits, each for providing adifferent output potential, and speed control switch means, connectedbetween said plurality of voltage dividers and said means for varyingthe current for coupling said means for varying the current to each ofsaid voltage dividers, and

wherein said means for compensating comprises a plurality of taps oneach of said plurality of said exciting windings and a plurality ofswitch means one coupled to each of said windings, each switch meanshaving a number of fixed terminals corresponding to the number of tapson its associated winding and a moveable contact for selectivelyconnecting said driving transistors to one of the taps of each of saidplurality of windings.

3. The Hall motor of claim 2 further comprising, means connecting saidplurality of moveable contacts to said speed control switch means forplacing said moveable contacts in an interlocking relationship with saidspeed control switch means.

4. A Hall motor as claimed in claim 3 further comprising double-poledouble-throw switches for changing the flow direction of excitingcurrent flowing through said exciting windings, two poles of each ofsaid switches being connected respectively to a 18 power source and thecollector of a corresponding one of said driving transistors.

1. A Hall motor of the type having a plurality of exciting windings,driving transistors for driving said windings and Hall elements forvarying the bias to the base circuits of said driving transistors, theinvention comprising, a. control means, including means for varying thecontrol current flowing in the Hall elements, to control the speed ofsaid motor, and b. means coupled to said exciting windings for varyingthe effective number of turns of said exciting windings in response todesired speed variations to compensate for the loss in efficiency on thevariation of motor speed.
 2. The Hall motor of claim 1 wherein saidcontrol means further includes, a plurality of voltage divider circuits,each for providing a different output potential, and speed controlswitch means, connected between said plurality of voltage dividers andsaid means for varying the current for coupling said means for varyingthe current to each of said voltage dividers, and wherein said means forcompensating comprises a plurality of taps on each of said plurality ofsaid exciting windings and a plurality of switch means one coupled toeach of said windings, each switch means having a number of fixedterminals corresponding to the number of taps on its associated windingand a moveable contact for selectively connecting said drivingtransistors to one of the taps of each of said plurality of windings. 3.The Hall motor of claim 2 further comprising, means connecting saidplurality of moveable contacts to said speed control switch means forplacing said moveable contacts in an interlocking relationship with saidspeed control switch means.
 4. A Hall motor as claimed in claim 3further comprising double-pole double-throw switches for changing theflow direction of exciting current flowing through said excitingwindings, two poles of each of said switches being connectedrespectively to a B power source and the collector of a correspondingone of said driving transistors.